Context-centric Security

Mohit Tiwari, Prashanth Mohan, Andrew Osheroff,

Hilfi Alkaff, Eric Love, Elaine Shi,

Dawn Song, Krste Asanović

UC Berkeley

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Context-centric Security

• Contexts are light-weight real-life events

– a conference hallway meeting, a birthday party

• User shares contexts with contacts

– policies not based on permissions or labels

• System infers all low-level details

– in contrast to current practice…

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App-centric Privacy: Problematic

• Permissions are abstruse

– SD Card, File systems,…

– 56 of 100+: dangerous

– Statically assigned

• App owns user’s data

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What a Dope!

Data-centric Privacy: Problematic

Data

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Principals Policies on Labels

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B’day Party

Class Project

Files Camera Microphone Wifi

Apps

Contexts

System resources

Users

Problem: User maps Contexts to Policies

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Bubbles: Context-centric Security

• Data clusters around real-world contexts.

• Privacy policy as access control on contexts.

• Apps run in Bubbles; cannot affect privacy.

B’day Party Class Project

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Using Bubbles

B’day Plans

Time-line 7

email a caterer?

Using Bubbles

B’day Catering

Time-line 8

Using Bubbles

B’day Party

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Caterer: not part of party bubble Two contexts within same event

A Bubble is the Minimum Unit of Sharing

• Untrusted code can arbitrarily mix data inside a bubble.

– Hence, sharing one item == sharing any item.

• Have to limit cross-bubble declassification

– So that user has flexibility of re-sharing, e.g. meeting notes

• Bubbles have to be very light-weight contexts

– I would put every 1:1 meeting at Usenix into a unique bubble

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Challenges in implementing Bubbles

• Lots of bubbles UI for navigating bubbles

• Apps don’t own data API for developers

• System implementation Infer dangerous permissions, and create light-weight containers

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Recent Bubbles

B’day Party B’day Plans B’day Catering

Bubbles Contacts 12

Local Bubbles

B’day Party

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Hike

Tilden

Sailing Henry Wharf

Farmers Market

Bubbles App Design Pattern

Developer Updates, Ads, …

Developer Zone

User

B’day Plan

B’day Party

Public profile info

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• Application-initiated sharing – Recommendation engines, Spam filters – Differential privacy, k-anonymity, …

• User-initiated sharing

– Storing, sharing, and editing docs – Real-time communication (voice, video)

• Anonymous: Not tied to real identity – Games, flashlights, wallpapers, – Browsing news, reviews, recipes, …

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Free Paid

Many Apps fit inside Bubbles Pe

rcen

t

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System Infers Dangerous Permissions

• User-controlled resources: 7

– location, camera, microphone, read-contacts

• Virtualized resource: 27

– internal and external storage, system logs, app cache and history,…

• Communication with firewall rules: 17

– internet access, wifi, telephony

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Context-centric Security

Bubbles Project

• Context = minimum unit of sharing data.

• Is working in contexts intuitive? Learnable?

• Does API support all useful functionality?

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